Apparatus for dispensing heat softenable adhesive initially in granule form

ABSTRACT

A dispenser for heat softenable adhesive initially in granule form has a hopper for receiving the granules of adhesive, a chamber for heat softening adhesive granules received from the hopper, a vessel for receiving softened adhesive from the chamber and a pump for supplying adhesive from the vessel as desired. The hopper has means for dispensing predetermined quantities of adhesive granules into the chamber. The chamber for heat softening the adhesive has progressively narrowing passages between heated members for heating the adhesive and, preferably, a piston for pressing adhesive along the passages. A control responsive to the level of adhesive in the vessel activates the hopper dispensing means and the chamber for heating the adhesive.

Q Umted States Patent [1 1 [111 3,773,069 Rebentisch Nov. 20, 1973 APPARATUS FOR DISPENSING HEAT 3,322,139 5 1967 Asano et a1 251 126 x SOFTENABLE ADHESIVE INITIALLY IN 3,587,930 6/1971 Schultz 222/146 HE GRANULE FORM FOREIGN PATENTS OR APPLICATIONS [76] Inventor: Hans Waldemar Rebentisch, 1,012,154 7/1957 Germany 222/146 HE Frankfurt am Main-Bonames, 681,749 3/1964 Canada 222/146 HE Germany Primary Examiner-Samuel Scott A U M C t B t M [73] Sslgnee S orpora OS on ass AttorneyRichard B. Megley et al. [22] Filed: Jan. 31, 1972 [21] Appl. No.: 222,099 [57] ABSTRACT A dispenser for heat softenable adhesive initially in [30] Foreign Application Pri rit D t granule form has a hopper for receiving the granules Feb. 3, 1971 Germany P 21 05 037.3 of adhesive, a chamber for heat Softening adhesive granules received from the hopper, a vessel for receiv- 52 US. Cl 137/341, 222/146 HE softened adhesive the chamber and 9 P 51 1111. C1. F16k 49/00 for SIPPlYing adhesive the vessel as desired' The 58 Field 61 Search 222/146 HE, 146 11s, hopper has means for dispensing predetermined 222 46 HA. 25 22 12 27; 37 34 tities Of adhesive granules into the chamber. The

chamber for heat softening the adhesive has progres- [56] References Cited sively narrowing passages between heated members for heating the adhesive and, preferably, a piston for UNITED STATES. PATENTS pressing adhesive along the passages. A control reg g i f 'g sponsive to the level of adhesive in the vessel activates 3:622:045 11/1971 Delaiie yfJr. 21111111111 222 146 HE the l dispe nsing means and the chamber 3,012,373 12 1961 Willis 1. 137 341 x heatmg the 2,809,772 10 1957 Weisz 222 146 HE 9 Claims 2 Drawing Figures 3,043,480 7/1962 Wittrock 222/146 HE 3,221,937 12/1965 Kamborian 222/146 HE APPARATUS FOR DISPENSING HEAT SOFTENABLE ADHESIVE INITIALLY IN GRANULE FORM BACKGROUND OF THE INVENTION Adhesives which are initially in granular form and are heat softenable into a melted, liquid form are commercially available. The granule or pellet form of the adhesive permits storage of a large amount of adhesive in a small space and, in the melted form, the adhesive is readily available for use. In many uses, as for example sealing paper cartons, only a small quantity of adhesive is needed for each individual application.

In the past, a quantity of adhesive granules has been melted in a crucible and the quantity of melted adhesive required for a particular application removed as needed. Not only do such systems require continual application of relatively large quantities of heat to maintain the adhesive in the crucible in the molten condition, but such systems also require melting in the crucible the entire quantity of adhesive needed over a long time for a succession of smaller applications, thus further increasing the heat required for the adhesive. Initially supplying heat sufficient to melt the adhesive in the relatively large quantities in the crucible takes a substantial amount of time and the adhesive maintained at the elevated temperature is often subject to heat degradation as by cracking where the heat softenable adhesive is an organic plastic.

Although only small quantities of adhesive may be required for each application, high production rates require substantially continual availability of heat softened, liquid adhesive. Solution of the heat problems of crucible melting of adhesives by melting only small quantities of adhesive often frustrates supplying adhesive in the quantities required for such high production rates.

SUMMARY OF THE INVENTION Accordingly, it is an object of the invention to provide apparatus for heat softening adhesive initially in a granular form which does not require maintenance of a large quantity of adhesive in a molten state and which nevertheless provides continuous availability of heat softened adhesive.

Apparatus for carrying out the invention comprises a hopper for receiving granulated, heat softenable adhesive. The hopper has means for dispensing predetermined quantities of adhesive into a chamber for heating. The chamber has heated members defining at least one progressively narrowing passage for receiving at the largest end of the passage granules of adhesives, heating the adhesive within the passage and discharging heat softened adhesive at the narrowest end of the passage. Means for causing granules of adhesive to enter and pass along the passages is preferably provided in the chamber. An outlet from the chamber communicates with a vessel for receiving heat softened adhesive and a pump removes adhesive from the vessel as required for use. Preferably, a control responsive to the level of the adhesive in the vessel is effective to control the operation of the means for dispensing the granules from the hopper into the chamber and the means for causing granules to enter the passage in the chamber.

DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention which is intended to be illustrative of and not a limitation on the invention will now be further described with reference to accompanying drawings of apparatus for carrying out the invention, in which:

FIG. 1 is a largely schematic view, partly in section, of apparatus for carrying out the method of the invention; and

FIG. 2 is a section view of an alternative embodiment of adhesive passage defining members shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT As seen in FIG. 1, a preferred apparatus for carrying out the invention comprises a hopper 1 an outlet portion of which is connected by a feed pipe 2 to a chamber generally designated 3. A quantity of adhesive granules 4 in the hopper is intermittently fed in predetermined quantities through the feed pipe into the chamber. An impeller 5 in the outlet portion of the hopper has uniformly spaced blades 6 for predetermining the quantities of adhesive granules fed into the chamber.

The feed pipe 2 enters the chamber in a central portion 7 having a piston 8 in movable, sealing engagement with side walls 9 of the chamber like a double acting pump. End walls 14 of the chamber toward and away from which the piston 8 may be moved have secured to them a plurality of conical, heated pins 10 having their longitudinal axes parallel to the direction of piston movement and the ends 16 of smallest diameter nearest the piston. Adjacent pins thus define a plurality of progressively narrowing passages 12 in the spaces between pins. The openings 18 of the passages adjacent the smallest diameter ends 16 of pins are preferably of a size substantially equal to the granules or just sufficient to accommodate the largest diameter of an adhesive granule 4, while the end 20 of the passage adjacent the largest diameter of the pins at the end wall 14 has dimensions less than the smallest diameter of an adhesive granule. Outlets 22, 23 from the chamber are provided adjacent the narrowest end 20 of the passage so that movement of the piston 8 toward either end wall 14 of the chamber will cause adhesive granules to enter the passage 12 and pass toward the outlets 22, 23 as the granules are heat softened and made molten by the heated pins 10.

Adhesive discharged from the chamber through the outlets 22, 23 is collected at atmospheric pressure in a vessel 24 from which it is conducted by pipe 27 under the action of pump 28. The pump 28 has a discharge outlet 34 from which melted adhesive is dispensed for use.

The hopper l is disposed above the chamber 3 so that adhesive granules will flow toward the chamber to fill the spaces between the blades 6 of the impeller in the hopper. The impeller is driven by a linear pneumatic motor 36 connected to the impeller by a radial arm 38 in driving relation with the blades of the impeller through a unidirectionally rotating clutch (not shown). Linear movement or stroke of the motor 36 is related to the spacing of the impeller blades 6 so as to incrementally rotate the impeller the number of degrees between adjacent impeller blades. The engagement between the impeller blades and the hopper is initially set so that stroke of linear movement of the motor will dispense the granules of adhesive between one pair of adjacent impeller blades for each stroke of the motor. A

predetermined quantity of granules per motor stroke is thus dispensed into the chamber. m

The piston 8 in the chamber is connected to a reciprocable linear motor 40 for movement from a position adjacent the smallest diameter ends 16 of one set of conical pins toward the other set. Since the chamber is symmetrical about a center line between the sets of pins, operation of the chamber in relation to only the right hand set of pins, as seen in FIG. 1, will be described; it is understood that operation in relation to the other set of pins is identical with that to be described.

Movement of the piston toward this set of pins, to the right as seen in FIG. 1, pushes granules of adhesive received from the hopper into the openings 18 between adjacent pins. The openings 18 are substantially equal to or just larger than the largest diameter of adhesive granules so that only one or a few granules will be received at any time in one passage defined between adjacent pins. This dimensional arrangement assures that a maximum surface area of adhesive granules per volume charge of adhesive granules will be in contact with or immediately adjacent the heat conducting pins 10. Heating means such as electrical cartridge heaters 41 are disposed within the pins 10 to heat the adhesive granules between the pins. Because the granules each contact a heated pin or pins, the apparatus does not rely upon heat conduction through the adhesive which often is a poor heat conductor.

As the granules are heated they beat soften and de form to pass along the progressively narrowing passages under the pressure of the piston 8 transmitted through successive granules. The piston and pins additionally mechanically work the adhesive while passing along the passages. When the adhesive reaches the nar' rowest end portion 20 of the passages, it has melted into substantially liquid condition and flows along or adjacent to the end wall 14 of the chamber between the pins to the outlet 22.

From the outlet 22 the adhesive flows under gravity into the vessel 24. Only relatively small quantities of adhesive may be retained in the vessel as an additional predetermined quantity of adhesive granules may be dispensed into the chamber and quickly melted by the pins to replace adhesive withdrawn from the vessel. To determine when replenishing adhesive must be supplied to the vessel, a control comprises a float 42 floating in adhesive in the vessel and connected to an arm pivoted to a wall of the vessel. When, intermittently, the adhesive level in the vessel drops, the arm releases a normally closed switch 44 outside the vessel to activate the impeller motor 36 and the piston motor 40. The motors 36 and 40 continue to operate until the level of adhesive in the vessel rises sufficiently to cause the arm of the float 42 to reclose the switch 44. The motors 36 and 40 are selected to have operating cycles such that adhesive granules will be fed into the chamber at an appropriate rate to be pressed into the passages in the chamber by the piston 8. Alternatively, timing control means for the motors may be provided to appropriately supply melted adhesive to the vessel.

Melted adhesive in the vessel is conducted by pipe 27 to the pump 28. The pump 28 has a spring-loaded ball valve 46 at the connection between the pipe and the pump which permits adhesive to flow into a piston chamber 48 of the pump when a piston 50 in the chamber moves away from the pipe inlet and to close the inlet to the pipe when the piston moves toward the inlet. When the piston moves toward the pipe inlet, a similar spring-loaded ball valve 52 opns to permit adhesive flow into a pressure chamber 54. A diaphragm 55 in a wall of the pressure chamber is deformed by pressure of adhesive in the pressure chamber to engage and open a normally closed switch 56 to terminate action of a reciprocating motor 58 connected to the piston 50. A substantially constant pressure supply of adhesive is thus provided at the outlet 34 from the pump. From the time the adhesive leaves the vessel until it is discharged from the pressure pump outlet 34, the adhesive need not be exposed to air which could cause a degradation of the adhesive.

In an alternative embodiment of the invention the pins Ml in the chamber 3 may be replaced by a block 69 in sealing engagement with side walls 9 of the chamber and spaced from the end walls 14 of the chamber so as to provide access to the outlet 22 adjacent the end walls of the chamber. The block 60 has a plurality of tapered bores having their largest dimensions adjacent the piston and smallest dimensions at their ends nearest the end walls 14. The largest dimension ends are again sized to accommodate only one or a few adhesive granules at a time so as to provide the greatest contact area to volume ratio for rapidly heating adhesive in the bores. The block is provided with heaters (not shown) to heat the adhesive in the bores. In still a further embodiment of the invention, the bores may be replaced by passages of noncircular cross-sectional shapes of appropriate size for admitting granules of adhesive.

It is understood that the invention is not limited to the particular preferred and alternative embodiments described and that other embodiments, such as the use of gravity to cause progress of adhesive along the passages, are within the scope of the invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

l. Apparatus for dispensing heat softenable adhesive initially in granular form, comprising: walls defining a chamber for receiving adhesive granules and having an outlet through one wall, pins within the chamber defining at least one progressively narrowing passage, said passage having a largest opening for receiving adhesive granules and a smallest end adjacent the outlet from the chamber, means for heating the pins defining the passage to heat soften adhesive in the passage; and a vessel adjacent the outlet for collecting the heat softened adhesive.

2. Apparatus as in claim 1 wherein the largest opening of the passage has cross-sectional dimensions substantially equal to the largest dimensions of an adhesive granule for admitting one or a few granules to the passage at a time.

3. Apparatus as in claim 1 wherein the pins defining 4 the passage are conical and have a largest diameter portion secured to a wall of the chamber.

4. Apparatus as in claim 1 and additionally comprising an incrementally rotated impeller for dispensing charges of a predetermined quantity of adhesive granules into the chamber and means responsive to the level of adhesive in the vessel for controlling the operation of the impeller.

5. Apparatus as in claim 1 wherein the pins are connected to each other at the narrowest end of the passage to form a block.

' the adhesive granules through the passage.

9. Apparatus for dispensing heat softenable adhesive initially in granular form, comprising: a hopper for receiving granules of adhesive; a chamber having an opening in a central portion thereof connected to the hopper for receiving adhesive granules from the hopper, an incrementally rotated impeller in the hopper for dispensing charges of a predetermined quantity of adhesive granules from the hopper into the chamber, a plurality of conical pins each having a largest diameter end secured to one of two opposite end walls of the chamber for defining progressively narrowing passages, means for heating the pins, a piston in the central portion of the chamber and reciprocable toward first one end wall of the chamber and then the other for pressing the adhesive granules in the central portion of the chamber into the passages at one end of the chamber and then the other to heat and soften the adhesive, and outlets adjacent the end walls of the chamber for dispensing the heat softened adhesive from the chamber. l 

1. Apparatus for dispensing heat softenable adhesive initially in granular form, comprising: walls defining a chamber for receiving adhesive granules and having an outlet through one wall, pins within the chamber defining at least one progressively narrowing passage, said passage having a largest opening for receiving adhesive granules and a smallest end adjacent the outlet from the chamber, means for heating the pins defining the passage to heat soften adhesive in the passage; and a vessel adjacent the outlet for collecting the heat softened adhesive.
 2. Apparatus as in claim 1 wherein the largest opening of the passage has cross-sectional dimensions substantially equal to the largest dimensions of an adhesive granule for admitting one or a few granules to the passage at a time.
 3. Apparatus as in claim 1 wherein the pins defining the passage are conical and have a largest diameter portion secured to a wall of the chamber.
 4. Apparatus as in claim 1 and additionally comprising an incrementally rotated impeller for dispensing charges of a predetermined quantity of adhesive granules into the chamber and means responsive to the level of adhesive in the vessel for controlling the operation of the impeller.
 5. Apparatus as in claim 1 wherein the pins are connected to each other at the narrowest end of the passage to form a block.
 6. Apparatus as in claim 1 and additionally comprising means for passing granules of adhesive through the passage.
 7. Apparatus as in claim 6 wherein the means for passing the adhesive granules through the passage is a piston.
 8. Apparatus as in claim 6 and additionally comrising means responsive to the level of adhesive in the vessel for controlling the operation of the means for passing the adhesive granules through the passage.
 9. Apparatus for dispensing heat softenable adhesive initially in granular form, comprising: a hopper for receiving granules of adhesive; a chamber having an opening in a central portion thereof connected to the hopper for receiving adhesive granules from the hopper, an incrementally rotated impeller in the hopper for dispensing charges of a predetermined quantity of adhesive granules from the hopper into the chamber, a plurality of conical pins each having a largest diameter end secured to one of two opposite end walls of the chamber for defining progressively narrowing passages, means for heating the pins, A piston in the central portion of the chamber and reciprocable toward first one end wall of the chamber and then the other for pressing the adhesive granules in the central portion of the chamber into the passages at one end of the chamber and then the other to heat and soften the adhesive, and outlets adjacent the end walls of the chamber for dispensing the heat softened adhesive from the chamber. 